anaerobic respiration

how can cells produce some some atp in low oxygen conditions via anaerobic pathways

cells can oxidise reduced NAD, produced in glycolysis, use this foe hydrogen transport - glycolysis continues

2 pathways used by cells to respire anaerobically in low oxygen conditions

ethanol fermentation and lactate fermentations

what types of organisms use ethanol fermentation to respire anaerobically

yeast and plants

what types of organisms/cells use lactate fermentation when respiring anaerobically

muscle cells and microorganisms

explain the process of ethanol fermentation (3)

1. pyruvate is converted to ethanal by the enzyme pyruvate decarboxylase - co2 is a by product

2. ethanal is reduced to ethanol and catalysed by ethanol dehydrogenase - NADH oxidised to NAD

explain the process of lactate fermentation ()

pyruvate is reduced to lactate by lactate dehydrogenase - NADH oxidised to NAD

ethanol dehydrogenase

enzyme that catalyses the reduction of ethanal to ethanol

pyruvate decarboxylase

enzyme that catalyses the conversion of pyruvate to ethanal

in anaerobic respiration in animals, pyruvate is reduced to

lactate

what 2 things can happen after lactate is produced

oxidised back to pyruvate- used in krebs cycle or converted into glycogen for storage in the liver

oxygen debt

oxidation of lactate back to pyruvate needs extra oxygen - breathe deeper to make up

what is a redox indicator

substance that changes colour when reduced or oxidised

2 examples of redox indicators

DCPIP and methylene blue

what are redox indicators such as DCPIP and methylene blue used to investigate in rqp 9

effects of temperature and substrate concentration on the rate of anaerobic respiration in yeast

where can the oxidised NAD produced in anaerobic respiration be used

in further glycolysis

identify substance A

pyruvate

identify substance B

ethanal

what reaction has occurred at point X, justify this (2)

1. reduction reaction

2. ethanal is the hydrogen acceptor

give 2 ways that lactate can be metabolised

1. oxidised to produce pyruvate

2. stored at glycogen

in an experiment to measure anaerobic respiration, a researcher uses an airtight container containing yeast. Why must the sealed container must be airtight (3)

1. no oxygen can enter

2. no co2 can escape

3. prevent entry of microorganisms

explain the relationship between the concentration of oxygen and co2 (2)

1. yeast are respiring aerobically

2. so oxygen used is equal to co2 produced

a bio fuel company want to know how long they should let the reaction go on for, when commercially producing ethanol for biofuels using substance L. use figure 1 to suggest a length of time - justify (3)

1. 7 hours

2. curve starts levelling off

3. becomes less cost-effective

after exercise, explain why blood lactate begins to fall (2)

1. lactate converted to pyruvate

2. lactate reacts with oxygen

what happens when dcpip or methylene blue are present in anaerobic respiration (rqp 9)

they take up hydrogens from the organic compounds and are reduced instead of NAD - changing from blue to colourless

what does the rate of colour change correspond to in rqp 9, when investigating the rate of anaerobic respiration in yeast

the rate dehydrogenase is working at, therefore rate of respiration yeast

(rqp 9) rate of respiration(sec-1) =

1/time (sec)

6 control variables of the yeast practical (rqp9)

volume of dye added, volume of yeast suspension, type of substrate, concentration of substrate, temperature and pH